The steam electrolysis between 800° and 950°C has been investigated with a cell consisting of the following elements: electrolyte, 400μ of ytterbia stabilized zirconia; anode, 100μ of vacuum deposited tin doped india; cathode, a sputter deposited cermet of nickel and urania doped ytterbia stabilized zirconia. These cells can be operated below 1.5V at 1 A/cm2 over 1000 hr.